GUIDs are used extensively with the Windows Installer to uniquely identify products, components, upgrades, and other key elements of the installation process. To generate GUIDs use the guidgen tool that ships with Visual Studio, generally located under Tools > Create GUID menu, or the GuidGen.com site. GUIDs generated this way will work fine in WiX, however since they are in mixed case they may cause issues if you share them with users of other, non-WiX tools. For complete compatibility be sure to change the letters in the GUID to uppercase prior to use.
All examples in the How To documentation use the text PUT-GUID-HERE for GUIDs. Every PUT-GUID-HERE must be replaced with a newly-generated GUID.
<Product Id="*" Version="126.96.36.199" Language="1033" Name="My Application Name" Manufacturer="My Manufacturer Name">
For the Component element the generated GUID is based on the install directory and filename of the KeyPath for the component. This GUID will stay consistent from build-to-build provided the directory and filename of the KeyPath do not change.